A detailed nuclear magnetic resonance investigation will be carried out on a series of selected model heme complexes and idealized hemoproteins, primarily in their paramagnetic states, in order to gain a quantitative understanding of the hyperfine shifts as probes for structure-function relationships in hemoproteins. The foundation of the project is the peak assignment of all hyperfine shifted protons, and the resolution and assignment of selected 13C resonances in both model compounds and hemoproteins, using a unique series of porphyrins with specific functional groups either deuterium-labelled or 13C-enriched. Based on model studies, several new probes for specific structural features, thought to be functionally relevant, will be tested in "model" proteins as well as selected hemoglobins. The monomeric, allosteric chironomus insect hemoglobins will serve as models for tertiary structural changes, and selected mutant hemoglobins will be utilized as models for effects of quaternary structural transitions. These structural probes will focus on imidazole-iron tension, iron-substrate bonding, and vinyl orientation/oscillatory mobility as an indicator of heme-protein interactions. The nature of the assigned methyl hyperfine shift spread or heme in-plane pi asymmetry in a variety of models and hemoproteins will be explored as a source of information on peripheral heme-apoprotein contacts, and as a monitor of the existence of heme disorder in both native and reconstituted hemoproteins. The possible role of distal residues in controlling ligand affinity will be investigated, and relaxation measurements of 13C peaks in oxy-hemoglobin will be performed to settle the question of the solution spin state and electronic structure.